Gets or sets the graph ordinal of this node - a number that roughly (but consistently)
represents its place in the execution order for this graph. Loopbacks' ordinals indicate
their place in the execution order as of their first execution.

Gets a value indicating whether this instance is simple. A node is simple if it
has one input and one output and performs no tasks beyond a pass-through. In the case
of a Step, a Simple step is a Null step. This also facilitates graph reduction.

Gets the SEID, or Source Element ID of this element. If the PFC of which
this element is a member is cloned, then this SEID will be the Guid of the element
in the source PFC that is semantically/structurally equivalent to this one.